46 C.F.R. § 64.47 Type of relief devices.
Title 46 - Shipping
(a) An MPT with an internal capacity of more than 550 U.S. gallons must have one or more spring loaded relief valves. In addition, a rupture disc may be attached. (b) An MPT with an internal capacity of 550 U.S. gallons or less must have a rupture disc or a spring loaded relief valve.
Title 46: Shipping
PART 64—MARINE PORTABLE TANKS AND CARGO HANDLING SYSTEMS
Subpart B—Standards for an MPT
§ 64.47 Type of relief devices.
